InnoSwitch3-CP
It is recommended that for compact power supply designs using an
InnoSwitch3-CP IC, triple insulated wire should be used.
IR
=
KP ≡ KRP
IP
Primary Layers, L
Primary layers should be in the range of 1 ≤ L ≤ 3 and in general
should be the lowest number that meets the primary current density
limit (CMA). A value of ≥200 Cmils / Amp can be used as a starting
point for most designs. Higher values may be required due to
thermal constraints. Designs with more than 3 layers are possible but
the increased leakage inductance and the physical fit of the windings
should be considered. A split primary construction may be helpful for
designs where clamp dissipation due to leakage inductance is too
high. In split primary construction, half of the primary winding is
placed on either side of the secondary (and bias) winding in a
sandwich arrangement. This arrangement is often disadvantageous
for low power designs as this typically increases common mode noise
and adds cost to the input filtering.
IR
IP
Primary
(a) Continuous, KP < 1
IP
IR
Primary
(b) Borderline Continuous/Discontinuous, KP = 1
PI-2587-103114
Figure 20. Continuous Conduction Mode Current Waveform, KP < 1.
(1-D) × T
KP ≡ KDP
=
t
T = 1/fS
Primary
(1-D) × T
D × T
t
Secondary
(a) Discontinuous, KP > 1
T = 1/fS
Primary
(1-D) × T = t
D × T
Secondary
(b) Borderline Discontinuous/Continuous, KP = 1
PI-2578-103114
Figure 21. Discontinuous Conduction Mode Current Waveform, KP > 1.
17
Rev. D 08/18
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